WO2021135814A1 - Isolation circuit, automobile diagnosis device, and automobile diagnosis system - Google Patents

Abstract

An isolation circuit (100), an automobile diagnosis apparatus (300), and an automobile diagnosis system (500). The isolation circuit (100) comprises: a first switch circuit (10), electrically connected between an OBD connector (111) of an automobile to be diagnosed and a diagnostic device (200) of the automobile diagnosis apparatus (300), wherein the OBD connector (111) is further electrically connected to an automobile power supply (112) of the automobile; and a switch control circuit (20), electrically connected to the OBD connector (111) and the first switch circuit (10), wherein the switch control circuit (20) does not operate when it is detected that the OBD connector (111) outputs a power supply positive signal and when it is not detected that the OBD connector (111) outputs a power supply negative signal, such that the first switch circuit (10) operates in an off state to ensure that the diagnostic device (200) is not powered on, and the switch control circuit (20) outputs a control signal when it is detected that the OBD connector (111) outputs a power supply positive signal and when it is detected that the OBD connector (111) outputs a power supply negative signal, such that the first switch circuit (10) operates in an on state to ensure that the automobile power supply (112) supplies power to the diagnostic device (200). In the invention, poor grounding is avoided, and the reliability of the automobile diagnosis apparatus (300) is improved.

Description

Isolation circuit, automobile diagnosis equipment and automobile diagnosis system

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on January 3, 2020, the application number is 202010006699.8, and the application name is "an isolation circuit, automotive diagnostic equipment and automotive diagnostic system", the entire content of which is incorporated by reference Incorporated in this application.

Technical field

This application relates to the field of automobile diagnosis, in particular to an isolation circuit, automobile diagnosis equipment and automobile diagnosis system.

Background technique

At present, the car diagnostic equipment is used to connect with the OBD connector of the car to be diagnosed, to read the fault code of the car to be diagnosed, and to locate the location and cause of the failure. However, if the car to be diagnosed uses a non-standard OBD connector, although the car to be diagnosed has no faults, the design size of the non-standard OBD connector differs from that of the standard OBD connector, which may cause the car diagnostic equipment to be connected to the OBD connector Poor grounding, that is, the positive pole of the car power supply is connected to the car diagnostic equipment before the negative pole of the car power supply, so that the instrument panel of the car to be diagnosed will turn on the fault light, which will easily interfere with the judgment of the car maintenance personnel.

Summary of the invention

The embodiments of the present invention aim to provide an isolation circuit, an automobile diagnostic equipment, and an automobile diagnostic system, which can avoid poor grounding and improve the reliability of the automobile diagnostic equipment.

To solve the above technical problems, the embodiments of the present invention provide the following technical solutions:

In the first aspect, an embodiment of the present invention provides an isolation circuit, which is applied to automobile diagnostic equipment, and the isolation circuit includes:

The first switch circuit is electrically connected between the OBD connector of the vehicle to be diagnosed and the diagnostic device of the vehicle diagnostic equipment, and the OBD connector is also electrically connected to the vehicle power supply of the vehicle to be diagnosed;

The switch control circuit is respectively electrically connected to the OBD connector and the first switch circuit, and is used to detect that the OBD connector outputs a positive signal of the power supply, and it is not detected that the OBD connector outputs a negative signal of the power supply , The switch control circuit does not work, so that the first switch circuit works in the off state, so as to keep the diagnostic device not powered on; when the OBD connector is detected to output the positive signal of the power supply, and all the signals are detected When the OBD connector outputs a negative signal of the power supply, it outputs a control signal to make the first switch circuit work in a conducting state, so that the vehicle power supply supplies power to the diagnostic device.

Optionally, the car power supply includes a car power supply positive electrode and a car power supply negative electrode, the car power supply positive electrode is used to output the power supply positive signal, the car power supply positive electrode is used to output the power supply negative signal, and the switch control circuit include:

A bias circuit, electrically connected to the positive pole of the automobile power supply, and used for converting the power supply voltage output by the positive pole of the automobile power supply into a bias voltage;

The second switch circuit is electrically connected to the positive pole of the vehicle power supply;

A step-down chopper circuit electrically connected to the second switch circuit, the negative pole of the automobile power supply, and the first switch circuit;

The controller is electrically connected to the positive pole of the automobile power supply, the negative pole of the automobile power supply, the bias circuit, the second switch circuit, and the step-down chopper circuit, and is used for detecting the OBD connector When the positive power signal is output, and the OBD connector is not detected to output the negative power signal, the controller does not work; when the OBD connector is detected to output the power positive signal, and the OBD connector is detected to output power In the case of a negative signal, the current detection signal flowing through the second switch circuit is detected, and a pulse width modulation signal is output according to the bias voltage and the current detection signal to control the working state of the second switch circuit. The step-down chopper circuit is made to output the control signal.

Optionally, the bias circuit includes a first resistor and a first capacitor;

One end of the first resistor is connected to the positive pole of the automobile power supply, one end of the first capacitor, and the second switch circuit, and the other end of the first resistor is connected to the other end of the first capacitor and the second switch circuit. Controller connection.

Optionally, the second switch circuit includes a PMOS tube, the gate of the PMOS tube is connected to the controller, the source of the PMOS tube is connected to the positive electrode of the vehicle power supply, and the drain of the PMOS tube is It is connected with the controller and the step-down chopper circuit.

Optionally, the step-down chopper circuit includes:

The freewheeling circuit is electrically connected to the second switch circuit and the negative pole of the automobile power supply, and is used for when the second switch circuit is working in the on state, the freewheeling circuit is working in the off state, and when the When the second switch circuit works in the off state, the freewheeling circuit works in the on state;

The charging and discharging circuit is electrically connected to the second switch circuit, the freewheeling circuit, the negative pole of the automobile power supply, and the first switch circuit, and is used to output a positive power signal when the OBD connector is detected, and When detecting that the OBD connector outputs the negative signal of the power supply, when the freewheeling circuit is in the off state, charging is performed, and when the freewheeling circuit is in the on state, discharging is performed to output the control Signal and send the control signal to the first switch circuit.

Optionally, the freewheeling circuit includes a diode, the anode of the diode is connected to the negative electrode of the automobile power supply, and the cathode of the diode is connected to the drain of the PMOS tube and the charging and discharging circuit.

Optionally, the charging and discharging circuit includes an inductor and a second capacitor;

One end of the inductor is connected to the cathode of the diode and the drain of the PMOS tube, and the other end of the inductor is connected to one end of the second capacitor and the first switch circuit; The other end is connected to the negative pole of the automobile power supply.

Optionally, the switch control circuit further includes a voltage sampling circuit, which is respectively electrically connected to the negative pole of the automobile power supply, the step-down chopper circuit, the first switch circuit, and the controller for sampling the A control signal, so that the controller feedbacks and adjusts the control signal.

Optionally, the second resistor and the third resistor of the voltage sampling circuit;

One end of the second resistor is connected to the step-down chopper circuit and the first switch circuit, and the other end of the second resistor is connected to one end of the third resistor and the controller; the first The other end of the three resistors is connected to the negative pole of the automobile power supply.

Optionally, the switch control circuit further includes an input filter circuit, which is electrically connected between the positive pole of the automobile power supply and the negative pole of the automobile power supply, and is used for filtering the power supply voltage.

Optionally, the input filter circuit includes a third capacitor, one end of the third capacitor is connected to the positive pole of the vehicle power supply, and the other end of the third capacitor is connected to the negative pole of the vehicle power supply.

Optionally, the isolation circuit further includes a slow-start circuit, which is electrically connected to the first switch circuit and the diagnostic device, respectively, and is used for correcting when the working state of the first switch circuit is switched to the conducting state. The power supply voltage output by the automobile power supply is processed for delay.

Optionally, the first switch circuit includes:

The first switch is electrically connected between the positive pole of the vehicle power supply and the diagnostic device, and is also electrically connected to the switch control circuit, for working in a conducting state according to the control signal;

The second switch is electrically connected between the negative pole of the automobile power supply and the diagnostic device, and is also electrically connected to the switch control circuit, and is used for working in a conducting state according to the control signal.

In the second aspect, an embodiment of the present invention provides an automobile diagnostic equipment, including:

The isolation circuit as described in any one of the above;

The diagnostic unit is electrically connected to the isolation circuit and is also in communication connection with the vehicle to be diagnosed, and is used to work according to the power supply voltage provided by the vehicle power supply of the vehicle to be diagnosed when the isolation circuit is working in the conducting state, And, obtain the diagnosis data of the vehicle to be diagnosed.

In the third aspect, an embodiment of the present invention provides an automobile diagnosis system, including:

Automobile diagnostic equipment as described above;

The upper computer is in communication connection with the car diagnostic equipment, and is used to display the diagnostic data sent by the car diagnostic equipment.

The beneficial effect of the present invention is that compared with the prior art, the embodiments of the present invention provide an isolation circuit, a car diagnostic equipment and a car diagnostic system, which are electrically connected to the OBD connector of the car to be diagnosed and the car through a first switch circuit. Between the diagnostic devices of the diagnostic equipment, the OBD connector is also electrically connected to the vehicle power supply of the vehicle to be diagnosed, and the switch control circuit is electrically connected to the OBD connector and the first switch circuit respectively, and is used to output the positive signal of the power supply when the OBD connector is detected. , And the OBD connector output power negative signal is not detected, the switch control circuit does not work, so that the first switch circuit works in the off state to keep the diagnostic device not powered on, and the OBD connector outputs the power positive signal when the OBD connector is detected , And when the OBD connector is detected to output the negative signal of the power supply, it outputs a control signal to make the first switch circuit work in a conductive state, so that the car power supply supplies power to the diagnostic device. Therefore, the embodiment of the present invention can avoid poor grounding and improve Reliability of automotive diagnostic equipment.

Description of the drawings

One or more embodiments are exemplified by the pictures in the corresponding drawings. These exemplified descriptions do not constitute a limitation on the embodiments. The elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the attached drawings do not constitute a scale limitation.

FIG. 1 is a schematic structural diagram of an automobile diagnosis system provided by an embodiment of the present invention;

2 is a schematic structural diagram of an automobile diagnostic equipment provided by an embodiment of the present invention;

3 is a schematic structural diagram of an isolation circuit provided by an embodiment of the present invention;

4 is a schematic structural diagram of an isolation circuit provided by another embodiment of the present invention;

5 is a schematic structural diagram of a switch control circuit provided by an embodiment of the present invention;

FIG. 6 is a schematic diagram of circuit connection of a switch control circuit provided by an embodiment of the present invention.

Detailed ways

In order to facilitate the understanding of the application, the application will be described in more detail below with reference to the drawings and specific implementations. It should be noted that when an element is expressed as being "connected" to another element, it may be directly connected to the other element, or one or more intermediate elements may exist in between. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance.

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field of the present invention. The terminology used in the specification of the present invention is only for the purpose of describing specific embodiments, and is not used to limit the present invention. The term "and/or" used in this specification includes any and all combinations of one or more related listed items.

In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

Please refer to FIG. 1, which is a schematic structural diagram of an automobile diagnosis system provided by an embodiment of the present invention. As shown in Fig. 1, the automobile diagnosis system 500 includes automobile diagnosis equipment 300 and an upper computer 400 as described in the following device embodiments. The upper computer 400 is in communication connection with the automobile diagnosis equipment 300 for displaying the Diagnostic data sent by the car diagnostic equipment 300.

The automobile diagnosis system provided by the embodiment of the present invention avoids the phenomenon of poor grounding through automobile diagnosis equipment, thereby improving the reliability of diagnosis.

Please refer to FIG. 2, which is a schematic structural diagram of an automobile diagnostic equipment provided by an embodiment of the present invention. As shown in FIG. 2, the automobile diagnostic equipment 300 includes an isolation circuit 100 and a diagnostic device 200 as described in the following circuit embodiments. The diagnostic device 200 is electrically connected to the isolation circuit 100, and is also communicatively connected to the vehicle 11 to be diagnosed, and is used to provide the vehicle power supply 112 of the vehicle 11 to be diagnosed when the isolation circuit 100 is in a conducting state. The power supply voltage is higher than the power supply voltage, and the diagnosis data of the vehicle 11 to be diagnosed is obtained.

Wherein, the vehicle to be diagnosed 11 includes an OBD connector 111, a vehicle power supply 112, and an on-board automatic diagnosis system (not shown). The car power supply 112 includes a car power supply positive electrode and a car power supply negative electrode. The car power supply positive electrode is used to output the power supply positive signal, and the car power supply positive electrode is used to output the power supply negative signal.

Inside the vehicle 11 to be diagnosed, the OBD connector 111 is electrically connected to the positive pole of the vehicle power supply and the negative pole of the vehicle power supply, respectively. When the automobile diagnostic equipment 300 is connected to the automobile 11 to be diagnosed, the OBD connector 111 is electrically connected to the isolation circuit 100 and is communicatively connected to the diagnostic device 200. If the OBD connector 111 is normally connected to the isolation circuit 100, the isolation circuit 100 is used to enable the automobile power supply 112 to provide power to the diagnostic device 200 through the isolation circuit 100, and when the diagnostic device 200 After power-on, the diagnostic data of the vehicle 11 to be diagnosed is obtained through the OBD connector 111; if the OBD connector 111 and the isolation circuit 100 are poorly grounded, the isolation circuit 100 is used to cut off the power supply of the vehicle 112 and the power supply circuit of the diagnostic device 200 to keep the diagnostic device 200 off.

The automobile power supply 112 is used to provide a low-voltage DC power supply (usually 12V for gasoline vehicles and 24V for diesel vehicles) for all electrical equipment in the automobile 11 to be diagnosed, so that all parts of the automobile 11 to be diagnosed can work normally. When the car diagnostic equipment 300 is connected to the car 11 to be diagnosed, the car power supply 112 is also used to provide power for the car diagnostic equipment 300.

The on-vehicle automatic diagnosis system is also electrically connected to the OBD connector 111 (not shown) for monitoring the vehicle 11 to be diagnosed, generating diagnostic data, and when the diagnostic device 200 is powered on, it passes through the The OBD connector 111 sends the diagnostic data to the diagnostic device 200.

Specifically, the power supply positive signal and the power supply negative signal reach the isolation circuit 100 through the OBD connector 111, and the isolation circuit 100 is used to detect the power supply positive signal and the power supply negative signal. When the OBD connector 111 outputs a positive power signal, and the OBD connector 111 does not detect a negative power signal, keep the diagnostic device 200 off; when it detects that the OBD connector 111 outputs a positive power When it is detected that the OBD connector 111 outputs a power negative signal, the automobile power supply 112 is enabled to supply power to the diagnostic device 200.

The automotive diagnostic equipment provided by the embodiment of the present invention can avoid poor grounding of the automotive diagnostic equipment through an isolation circuit, thereby improving the reliability of the automotive diagnostic equipment.

Please refer to FIG. 3, which is a schematic structural diagram of an isolation circuit provided by an embodiment of the present invention. As shown in FIG. 3, the isolation circuit 100 is applied to an automobile diagnostic equipment 300 and includes a first switch circuit 10 and a switch control circuit 20.

The first switch circuit 10 is electrically connected between the OBD connector 111 of the vehicle to be diagnosed 11 and the diagnostic device 200 of the vehicle diagnostic equipment 300, and the OBD connector 111 is also connected to the vehicle power supply of the vehicle to be diagnosed 11 112 electrical connection.

Please refer to FIG. 4 and FIG. 5, the first switch circuit 10 includes a first switch 101 and a second switch 102.

The first switch 101 is electrically connected between the positive pole of the vehicle power supply and the diagnostic device 200, and is also electrically connected to the switch control circuit 20, for operating in a conducting state according to the control signal.

The second switch 102 is electrically connected between the negative pole of the vehicle power supply and the diagnostic device 200, and is also electrically connected to the switch control circuit 20, for operating in a conducting state according to the control signal.

In this embodiment, the first switch 101 and the second switch 102 are normally closed switches. It works in a conducting state according to the control signal, and when the controller 204 is not working, it returns to a normally closed state.

It can be understood that when the first switch 101 and the second switch 102 are both working in the on state, the first switch 101 and the second switch 102 pass through the OBD connector 111 of the vehicle 11 to be diagnosed. Are respectively electrically connected to the positive pole of the vehicle power supply and the negative pole of the vehicle power supply, so that the power supply voltage provided by the vehicle power supply 112 of the vehicle to be diagnosed 11 passes through the OBD connector 111 and reaches the first switch 101, the The second switch 102 and the switch control circuit 20 provide power for the first switch 101, the second switch 102, and the switch control circuit 20.

In some embodiments, the first switch 101 and the second switch 102 include a metal-oxide semiconductor field effect transistor, a bipolar transistor, a relay, a switch circuit composed of other transistors, and the like. At this time, when the controller 204 is not working, the output pins of the controller 204 corresponding to the first switch 101 and the second switch 102 are set low, and the switch control circuit 20 does not output a control signal , So that the first switch 101 and the second switch 102 work in the off state; when the controller 204 works, the controller 204 and the first switch 101 and the second switch 102 The corresponding output pin outputs a pulse width modulation signal, and the switch control circuit 20 outputs a control signal to make the first switch 101 and the second switch 102 work in a conducting state.

The switch control circuit 20 is electrically connected to the OBD connector 111 and the first switch circuit 10, respectively, for outputting a positive power signal when the OBD connector 111 is detected, and the OBD connector is not detected 111 when the negative signal of the power supply is output, the switch control circuit 20 does not work, so that the first switch circuit 10 works in the off state to keep the diagnostic device 200 off; when the OBD connector is detected 111 outputs the positive signal of the power supply, and when it is detected that the OBD connector 111 outputs the negative signal of the power supply, it outputs a control signal to make the first switch circuit 10 work in the conducting state, so that the automobile power supply 112 is the The diagnostic device 200 supplies power.

Wherein, the switch control circuit 20 detects that the OBD connector 111 outputs the positive signal of the power supply, and fails to detect the negative signal of the OBD connector 111 outputting the power supply, including the following situations: the positive pole of the automobile power supply is connected before the negative pole of the automobile power supply. Into the isolation circuit 100. The switch control circuit 20 detects that the OBD connector outputs a positive signal of the power supply, and detects that the OBD connector outputs a negative signal of the power supply, including the following two situations: 1. The positive pole of the automobile power supply and the negative pole of the automobile power supply are connected at the same time. The isolation circuit 100; 2. After the positive pole of the vehicle power supply is connected to the isolation circuit 100 at the negative pole of the vehicle power supply.

It can be seen that when the switch control circuit 20 detects that the OBD connector 111 outputs a positive power signal, and does not detect that the OBD connector 111 outputs a negative power signal, at this time, the positive pole of the automobile power supply is the switch control circuit 20. Provides input voltage. Since the switch control circuit 20 is not grounded, the switch control circuit 20 does not work, so that the first switch circuit 10 works in an off state to cut off the automobile power supply 112 and the diagnostic device 200 The power supply loop keeps the diagnostic device 200 unpowered. Then, artificially adjust the connection between the car diagnostic device 300 and the OBD connector 111, for example, re-plug the car diagnostic device 300, so that when the switch control circuit 20 detects that the OBD connector outputs a positive signal , And it is detected that the OBD connector outputs the negative signal of the power supply. At this time, the positive pole of the vehicle power supply provides the input voltage for the switch control circuit 20, the switch control circuit 20 is grounded, and the switch control circuit 20 outputs a control signal , Making the first switch circuit 10 work in a conducting state according to the control signal, so that the automobile power supply 112 provides power to the diagnostic device 200 through the isolation circuit 100. Therefore, it is avoided that poor grounding causes the voltage to rise or spark discharge, which causes the vehicle 11 to be diagnosed to detect an external high voltage pulse and trigger an alarm.

Please refer to FIG. 5 again. The switch control circuit 20 includes a bias circuit 201, a second switch circuit 202, a step-down chopper circuit 203, a controller 204, a voltage sampling circuit 205, and an input filter circuit 206.

The bias circuit 201 is electrically connected to the positive pole of the automobile power supply for converting the power supply voltage output by the positive pole of the automobile power supply into a bias voltage.

Please also refer to FIG. 6, the bias circuit 201 includes a first resistor R1 and a first capacitor C1.

Wherein, one end of the first resistor R1 is connected to the positive pole of the vehicle power supply, one end of the first capacitor C1, and the second switch circuit 202, and the other end of the first resistor R1 is connected to the first capacitor. The other end of C1 is connected to the controller 204.

The controller 204 includes a constant current source for providing a constant current i. The constant current i forms a voltage drop across the first resistor R1, that is, a bias voltage V, where the bias voltage V=R1*i, And, the bias voltage V is sent to the controller 204. In addition, the power supply voltage starts slowly under the action of the volume of the first resistor R1 and the first capacitor C1 to avoid the influence of spike voltage on the controller 204 and protect the controller 204 from being burnt out.

The second switch circuit 202 is electrically connected to the positive pole of the automobile power supply.

Wherein, the second switch circuit 202 includes a PMOS tube Q1, the gate of the PMOS tube Q1 is connected to the controller 204, the source of the PMOS tube Q1 is connected to the positive electrode of the vehicle power supply, and the PMOS tube The drain of Q1 is connected to the controller 204 and the step-down chopper circuit 203.

In some embodiments, the second switch circuit 202 further includes components such as resistors and/or capacitors, which are used to limit the gate-source voltage of the PMOS transistor Q1 and prevent the PMOS transistor Q1 from being affected by the excessively high gate-source voltage. breakdown.

The step-down chopper circuit 203 is electrically connected to the second switch circuit 202, the negative pole of the automobile power supply, and the first switch circuit 10, respectively.

In this embodiment, the step-down chopper circuit 203 includes a freewheeling circuit 2031 and a charging and discharging circuit 2032.

The freewheeling circuit 2031 is electrically connected to the second switch circuit 202 and the negative electrode of the automobile power supply, and is used for turning off the freewheeling circuit 2031 when the second switch circuit 202 is working in the on state. When the second switch circuit 202 is in the off state, the freewheeling circuit 2031 is in the on state.

As shown in FIG. 6, the freewheeling circuit 2031 includes a diode D1, the anode of the diode D1 is connected to the negative electrode of the automobile power supply, the cathode of the diode D1 is connected to the drain of the PMOS transistor Q1 and the charge and discharge Circuit 2032 is connected.

The charging and discharging circuit 2032 is electrically connected to the second switch circuit 202, the freewheeling circuit 2031, the negative pole of the automobile power supply, and the first switch circuit 10, respectively, for detecting the OBD connector 111 When the positive signal of the power supply is output, and the OBD connector 111 is detected to output the negative signal of the power supply, when the freewheeling circuit 2031 is working in the off state, charging is performed, and when the freewheeling circuit 2031 is working in the on state , The discharge is performed to output the control signal, and send the control signal to the first switch circuit 10.

As shown in FIG. 6, the charging and discharging circuit 2032 includes an inductor L1 and a second capacitor C2.

Wherein, one end of the inductor L1 is connected to the cathode of the diode D1 and the drain of the PMOS transistor Q1, and the other end of the inductor L1 is connected to one end of the second capacitor C2 and the first switch circuit 10 Connection; the other end of the second capacitor C2 is connected to the negative pole of the vehicle power supply.

Specifically, the pulse width modulation signal is used to modulate the duty cycle of the PMOS transistor Q1. When the PMOS transistor Q1 is in the on-ton period, the diode D1 is reverse-biased, and the power supply voltage is charged through the inductor L1 to charge the first switch circuit 10. At this time, the current flowing through the inductor L1 If iL increases, the energy storage of the inductor L1 increases. Assuming that the power supply voltage is E and the voltage across the first switch circuit 10 is u0, then there is a forward voltage Ul=E across the inductor L1 -u0, Ul makes the current iL increase linearly. When the PMOS transistor Q1 is in the off toff period, the inductor L1 generates an induced electromotive force, the diode D1 is turned on, and the current iL flows through the diode D1. At this time, Ul=-u0, and the inductor L1 The first switch circuit 10 is powered, the inductive energy storage is gradually consumed, and the current iL decreases linearly.

It can be understood that the inductance value of the inductor L1 and the capacitance value of the second capacitor C2 need to be set slightly larger. In this embodiment, the controller 204 outputs the pulse width modulation signal when detecting that the OBD connector 111 outputs a positive power signal and detects that the OBD connector 111 outputs a negative power signal. The PMOS transistor Q1 is modulated so that the charge and discharge circuit 2032 outputs the control signal according to the duty ratio of the PMOS transistor Q1. Wherein, the control signal is a sine wave signal, and the amplitude of the control signal can be changed by setting the duty ratio of the pulse width modulation signal.

The controller 204 is electrically connected to the positive pole of the automobile power supply, the negative pole of the automobile power supply, the bias circuit 201, the second switch circuit 202, and the step-down chopper circuit 203 for detecting When the OBD connector 111 outputs a power positive signal, and the OBD connector 111 does not detect that the OBD connector 111 outputs a power negative signal, the controller 204 does not work; when it is detected that the OBD connector 111 outputs a power positive signal, and When it is detected that the OBD connector 111 outputs the negative signal of the power supply, the current detection signal flowing through the second switch circuit 202 is detected, and a pulse width modulation signal is output according to the bias voltage and the current detection signal to control The operating state of the second switch circuit 202 is such that the step-down chopper circuit 203 outputs the control signal.

It can be understood that the controller 204 calculates the internal voltage drop formed by the PMOS transistor Q1 in the controller 204 according to the current detection signal, and the controller 204 calculates the internal voltage drop of the PMOS transistor Q1 according to the bias voltage and the PMOS transistor Q1. The internal voltage drop of the output pulse width modulation signal.

In this embodiment, the controller 204 includes a single-chip microcomputer, and the single-chip microcomputer may adopt 51 series, Arduino series, STM32 series, and the like.

Wherein, the single-chip microcomputer includes an input pin, an adjustable voltage pin, a current detection pin, an output pin, a power ground pin, a controller ground pin, and a feedback pin. The input pin is electrically connected to the positive pole of the vehicle power supply for receiving the power supply voltage; the adjustable voltage pin is electrically connected to the bias circuit 201 for receiving the bias voltage; The current detection pin is electrically connected to the second switch circuit 202 and the step-down chopper circuit 203 for obtaining the current detection signal; the output pin is electrically connected to the second switch circuit 202 for To output the pulse width modulation signal; the power ground pin is connected to the negative pole of the vehicle power supply; the controller ground pin is connected to the negative pole of the vehicle power supply; the feedback pin is connected to the voltage sampling circuit 205 The electrical connection is used to receive the voltage sampling signal sent by the voltage sampling circuit 205.

In some embodiments, the controller 204 may also be a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), an ARM (Acorn RISC Machine) or other Programmable logic device, discrete gate or transistor logic, discrete hardware components or any combination of these components; it can also be any traditional processor, controller, microcontroller or state machine; it can also be implemented as a combination of computing devices, For example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

The voltage sampling circuit 205 is electrically connected to the negative pole of the automobile power supply, the step-down chopper circuit 203, the first switch circuit 10, and the controller 204, and is used to sample the control signal so that all The controller 204 feeds back and adjusts the control signal.

As shown in FIG. 6, the voltage sampling circuit 205 has a second resistor R2 and a third resistor R3.

Wherein, one end of the second resistor R2 is connected to the step-down chopper circuit 203 and the first switch circuit 10, and the other end of the second resistor R2 is connected to one end of the third resistor R3 and the The controller 204 is connected; the other end of the third resistor R3 is connected to the negative pole of the vehicle power supply.

Specifically, the second resistor R2 and the third resistor R3 form a voltage divider circuit, divide the control signal, output a voltage sampling signal, and send the voltage sampling signal to the controller 204, so that the controller 204 feedback and adjusts the control signal according to the voltage sampling signal.

The input filter circuit 206 is electrically connected between the positive pole of the automobile power supply and the negative pole of the automobile power supply for filtering the power supply voltage.

The input filter circuit 206 includes a third capacitor C3, one end of the third capacitor C3 is connected to the positive pole of the vehicle power supply, and the other end of the third capacitor C3 is connected to the negative pole of the vehicle power supply. The third capacitor C3 is specifically used to filter out spikes and ripple voltages input by the automobile power supply 112, so that the signal waveforms of the power supply voltage input to the bias circuit 201 and the second switch circuit 202 smooth.

In some embodiments, the input filter circuit 206 is composed of reactive elements, for example, a capacitor is connected in parallel at both ends of the load, or an inductor is connected in series with the load, as well as various multiple filter circuits composed of capacitors and inductors.

It can be understood that the voltage sampling circuit 205 and/or the input filter circuit 206 may be omitted.

In some embodiments, referring to FIG. 4, the isolation circuit 100 further includes a slow-start circuit 40, which is electrically connected to the first switch circuit 10 and the diagnostic device 200, and is used for connecting to the first switch circuit 10 and the diagnostic device 200. When the working state of 10 is switched to the on state, the power supply voltage output by the automobile power supply 112 is delayed.

It can be understood that at the moment when the first switch circuit 10 is turned on, a high-voltage spike is generated. If the power supply voltage output by the automobile power supply 112 directly acts on the diagnostic device 200 through the first switch circuit 10, the high-voltage The spike pulse is also input to the diagnostic device 200, which may burn out or break down the internal components of the diagnostic device 200. The slow-start circuit 40 is used to delay processing the power supply voltage output by the automobile power supply 112 to prevent the high-voltage spikes from reaching the diagnostic device 200 and improve the safety of the isolation circuit 100.

The embodiment of the present invention provides an isolation circuit, which is electrically connected between the OBD connector of the car to be diagnosed and the diagnostic device of the car diagnostic equipment through a first switch circuit. The OBD connector is also electrically connected to the car power supply of the car to be diagnosed. The switch control circuit is electrically connected to the OBD connector and the first switch circuit respectively, and is used for detecting that the OBD connector outputs the positive signal of the power supply, and the OBD connector outputs the negative signal of the power supply, the switch control circuit does not work to make The first switch circuit works in the off state to keep the diagnostic device not powered on. When it detects that the OBD connector outputs a positive signal of the power supply, and detects that the OBD connector outputs a negative signal of the power supply, it outputs a control signal to enable the first switch The circuit works in a conducting state, so that the vehicle power supply supplies power to the diagnostic device. Therefore, the embodiment of the present invention can avoid poor grounding and improve the reliability of the vehicle diagnostic equipment.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them; under the idea of the present invention, the technical features of the above embodiments or different embodiments can also be combined. The steps can be implemented in any order, and there are many other variations of the different aspects of the present invention as described above. For the sake of brevity, they are not provided in the details; although the present invention has been described in detail with reference to the foregoing embodiments, it is common in the art The skilled person should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or equivalently replace some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the implementations of the present invention. Examples of the scope of technical solutions.

Claims (15)

1. An isolation circuit applied to automobile diagnostic equipment, characterized in that the isolation circuit includes:

   The first switch circuit is electrically connected between the OBD connector of the vehicle to be diagnosed and the diagnostic device of the vehicle diagnostic equipment, and the OBD connector is also electrically connected to the vehicle power supply of the vehicle to be diagnosed;

   The switch control circuit is respectively electrically connected to the OBD connector and the first switch circuit, and is used to detect that the OBD connector outputs a positive signal of the power supply, and it is not detected that the OBD connector outputs a negative signal of the power supply , The switch control circuit does not work, so that the first switch circuit works in the off state, so as to keep the diagnostic device not powered on; when the OBD connector is detected to output the positive signal of the power supply, and all the signals are detected When the OBD connector outputs a negative signal of the power supply, it outputs a control signal to make the first switch circuit work in a conducting state, so that the vehicle power supply supplies power to the diagnostic device.
2. The isolation circuit according to claim 1, wherein the car power supply includes a car power supply positive electrode and a car power supply negative electrode, the car power supply positive electrode is used to output the power supply positive signal, and the car power supply positive electrode is used to output the For the negative signal of the power supply, the switch control circuit includes:

   A bias circuit, electrically connected to the positive pole of the automobile power supply, and used for converting the power supply voltage output by the positive pole of the automobile power supply into a bias voltage;

   The second switch circuit is electrically connected to the positive pole of the vehicle power supply;

   A step-down chopper circuit electrically connected to the second switch circuit, the negative pole of the automobile power supply, and the first switch circuit;

   The controller is electrically connected to the positive pole of the automobile power supply, the negative pole of the automobile power supply, the bias circuit, the second switch circuit, and the step-down chopper circuit, and is used for detecting the OBD connector When the positive power signal is output, and the OBD connector is not detected to output the negative power signal, the controller does not work; when the OBD connector is detected to output the power positive signal, and the OBD connector is detected to output power In the case of a negative signal, the current detection signal flowing through the second switch circuit is detected, and a pulse width modulation signal is output according to the bias voltage and the current detection signal to control the working state of the second switch circuit. The step-down chopper circuit is made to output the control signal.
3. The isolation circuit according to claim 2, wherein the bias circuit comprises a first resistor and a first capacitor;

   One end of the first resistor is connected to the positive pole of the automobile power supply, one end of the first capacitor, and the second switch circuit, and the other end of the first resistor is connected to the other end of the first capacitor and the second switch circuit. Controller connection.
4. The isolation circuit according to claim 2, wherein the second switch circuit comprises a PMOS tube, the gate of the PMOS tube is connected to the controller, and the source of the PMOS tube is connected to the car power supply. The anode is connected, and the drain of the PMOS tube is connected to the controller and the step-down chopper circuit.
5. The isolation circuit according to claim 4, wherein the step-down chopper circuit comprises:

   The freewheeling circuit is electrically connected to the second switch circuit and the negative pole of the automobile power supply, and is used for when the second switch circuit is working in the on state, the freewheeling circuit is working in the off state, and when the When the second switch circuit works in the off state, the freewheeling circuit works in the on state;

   The charging and discharging circuit is electrically connected to the second switch circuit, the freewheeling circuit, the negative pole of the automobile power supply, and the first switch circuit, and is used to output a positive power signal when the OBD connector is detected, and When detecting that the OBD connector outputs the negative signal of the power supply, when the freewheeling circuit is in the off state, charging is performed, and when the freewheeling circuit is in the on state, discharging is performed to output the control Signal and send the control signal to the first switch circuit.
6. The isolation circuit according to claim 5, wherein the freewheeling circuit comprises a diode, the anode of the diode is connected to the negative electrode of the vehicle power supply, and the cathode of the diode is connected to the drain of the PMOS tube and the The charging and discharging circuit is connected.
7. The isolation circuit according to claim 6, wherein the charging and discharging circuit comprises an inductor and a second capacitor;

   One end of the inductor is connected to the cathode of the diode and the drain of the PMOS tube, and the other end of the inductor is connected to one end of the second capacitor and the first switch circuit; The other end is connected to the negative pole of the automobile power supply.
8. The isolation circuit according to claim 2, wherein the switch control circuit further comprises a voltage sampling circuit, which is respectively connected with the negative pole of the automobile power supply, the step-down chopper circuit, the first switch circuit, and the The controller is electrically connected to sample the control signal so that the controller can feedback and adjust the control signal.
9. The isolation circuit according to claim 8, wherein the second resistor and the third resistor of the voltage sampling circuit;

   One end of the second resistor is connected to the step-down chopper circuit and the first switch circuit, and the other end of the second resistor is connected to one end of the third resistor and the controller; the first The other end of the three resistors is connected to the negative pole of the automobile power supply.
10. The isolation circuit according to claim 8, wherein the switch control circuit further comprises an input filter circuit, which is electrically connected between the positive pole of the automobile power supply and the negative pole of the automobile power supply, and is used to perform the operation on the power supply voltage. Filtering processing.
11. The isolation circuit according to claim 10, wherein the input filter circuit comprises a third capacitor, one end of the third capacitor is connected to the positive electrode of the vehicle power supply, and the other end of the third capacitor is connected to the Car power negative connection.
12. The isolation circuit according to any one of claims 1-11, wherein the isolation circuit further comprises a slow-start circuit, which is electrically connected to the first switch circuit and the diagnostic device, respectively, for use in the When the working state of the first switch circuit is switched to the on state, the power supply voltage output by the automobile power supply is delayed.
13. The isolation circuit according to any one of claims 2-11, wherein the first switch circuit comprises:

    The first switch is electrically connected between the positive pole of the vehicle power supply and the diagnostic device, and is also electrically connected to the switch control circuit, for working in a conducting state according to the control signal;

    The second switch is electrically connected between the negative pole of the automobile power supply and the diagnostic device, and is also electrically connected to the switch control circuit, and is used for working in a conducting state according to the control signal.
14. An automobile diagnostic equipment, which is characterized in that it comprises:

    The isolation circuit according to any one of claims 1-13;

    The diagnostic unit is electrically connected to the isolation circuit and is also in communication connection with the vehicle to be diagnosed, and is used to work according to the power supply voltage provided by the vehicle power supply of the vehicle to be diagnosed when the isolation circuit is working in the conducting state, And, obtain the diagnosis data of the vehicle to be diagnosed.
15. An automobile diagnostic system, which is characterized in that it comprises:

    The automobile diagnostic equipment according to claim 14;

    The upper computer is in communication connection with the car diagnostic equipment, and is used to display the diagnostic data sent by the car diagnostic equipment.

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